dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Jun 01, 2010 at 06:57:33PM +0100, Garth N. Wells wrote:
>
>
> On 01/06/10 18:51, Anders Logg wrote:
> >On Tue, Jun 01, 2010 at 05:13:11PM +0100, Garth N. Wells wrote:
> >>
> >>
> >>On 01/06/10 17:07, Anders Logg wrote:
> >>>On Tue, Jun 01, 2010 at 03:19:50PM +0100, Garth N. Wells wrote:
> >>>>
> >>>>
> >>>>On 01/06/10 15:10, Anders Logg wrote:
> >>>>>What is the difference from before? Is it only that the dofs are
> >>>>>always tabulated and stored (never computed on the fly)?
> >>>>>
> >>>>
> >>>>More or less. There are some bug fixes and some missing features
> >>>>have been added (collapsed dof maps for renumbered maps, work in
> >>>>parallel now).
> >>>>
> >>>>It was too complicated (for me at least) to have both tabulated dofs
> >>>>and on the fly computation via UFC in the same class. It's much
> >>>>easier to follow now (which helped in finding some bugs).
> >>>>
> >>>>Garth
> >>>
> >>>Can you remind me of what collapse do? What is a contiguous dofmap?
> >>>
> >>
> >>A sub-dofmap will be, by default, a view into the original dof map.
> >>It will extract the the relevant indices, but it won't change them.
> >>It's suitable for when the sub-function shares the vector with the
> >>original equation, e.g.
> >>
> >>   Function&  u = U[0];
> >>   Function&  p = U[1];  // U, u and p shared the same vector
> >>
> >>A collapsed dof map is independent of the original dof map, with the
> >>lowest index = 0 and the greatest = global_dimension -1. It's used
> >>when a sub-function is extracted from a Function such that it has
> >>it's own vector, e.g.
> >>
> >>   Function u = U[0]; // u has its own vector
> >>   Function p = U[1]; // p has its own vector
> >>
> >>Garth
> >
> >ok. And is it the case that if the dof map has not been renumbered,
> >then collapsing it is the same as subtracting the offset,
>
> Yes.
>
> >but when it
> >has been renumbered, a new numbering will be computed?
> >
>
> Yes, and a map from the ufc dof index (as given by the ufc_dofmap
> object) to the actual dof index.

Why is that map needed? If the dof map has been renumbered (in build),
why do we need to ever think about the old UFC dof map?

--
Anders

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